CONVERGENT ‘CUTENESS’ IS MAKING DOGS AND CATS LOOK ALIKE

Pugs, Persian cats, and other smushed-face cats and dogs are more similar to one another than they are to the wild animals they evolved from.

What do Persian cats, pugs, and Pekingese dogs have in common? All three share an extreme skull shape: flat faces, bulging eyes, and noses pushed up between their eyes. This dramatic look isn’t natural—it’s the result of generations of selective breeding designed to mimic the baby-like features humans find cute.

But the consequences of this artificial design are becoming harder to ignore.

According to new research published in Proceedings of the National Academy of Sciences USA, the skulls of brachycephalic (short-headed) cats and dogs have become more similar to each other than to their wild ancestors—wolves and wildcats. It’s a striking case of human-driven convergent evolution.

“Wolves and wild cats have very distinct skulls,” says senior author Jonathan Losos, an evolutionary biologist at Washington University in St. Louis. “But by selecting for infant-like faces, we’ve made brachycephalic dogs and cats evolve to look more like each other than like their own wild relatives. We’ve effectively erased 50 million years of evolution.”

Selective Breeding, Not Natural Evolution

Typically, convergent evolution happens in nature when unrelated species adapt to similar environments—like how both bats and birds evolved wings, or how marine animals keep evolving into crab-like forms. But in this case, the driving force isn’t survival. It’s human taste.

“These skull shapes didn’t arise naturally—they exist only because humans prefer the way they look,” says lead author Abby Grace Drake, an evolutionary biologist at Cornell University.

Unfortunately, this aesthetic preference comes at a steep cost for the animals. Brachycephalic pets like pugs and Persians often suffer from serious health problems: chronic breathing difficulties, heat intolerance, dental issues, eye injuries, and even neurological complications. Many require surgery just to breathe properly.

“We’re breeding them to look cute, but we’re also breeding them to suffer,” says Drake. “They could never survive in the wild.”

Flattened Faces, Flattened History

Drake, Losos, and their team set out to better understand the range of skull shapes across cats and dogs. They analyzed skull measurements from 1,810 animals, using CT scans from animal hospitals and specimens from natural history museums. Their sample included 148 domestic cats and 677 dogs, both purebred and mixed breeds.

They identified eight extremely brachycephalic dog breeds—including pugs, bulldogs, and Pekingese—and three cat breeds: Persians, Himalayans, and Burmese. They also compared these skulls with those of hundreds of wild species from the Canidae (dog) and Felidae (cat) families.

Using 3D modelling, the researchers mapped key anatomical points on each skull. The results were clear: brachycephalic breeds, regardless of species, shared more in common with each other than with their evolutionary cousins. Their skulls have a drastically shortened nasal cavity, a tilted palate, and a compressed airway. Some Persian cats didn’t have nasal bones at all.

“These are skull shapes that never existed before we created them,” Drake explains. “It’s evolution on fast-forward—but at a cost.”

Health Before Aesthetics

From a scientific standpoint, the rapid transformation of these breeds is fascinating. It shows just how quickly traits can change when humans control the gene pool. But the researchers are unanimous: the health and welfare of the animals should come first.

“The ability to reshape evolution in this way is remarkable,” says Losos. “But that doesn’t mean we should do it.”

One future direction for research is identifying the specific genes responsible for these skull shapes. There’s evidence that the genetic causes of brachycephaly differ between cats and dogs. Understanding those differences could help reduce suffering.

Geneticist Heather Lorimer of Youngstown State University, who was not involved in the study, agrees. “A detailed study like this sets the stage for pinpointing genes that influence skull development,” she says. “That knowledge could lead to more responsible breeding practices focused on health rather than appearance.”

A Better Way to Adopt

For those concerned about animal welfare, Drake offers a simple piece of advice: adopt a mixed-breed pet from a shelter.

“They’re generally healthier, and you won’t be supporting the continuation of traits that cause suffering,” she says.

Flat-faced pets may look adorable—but their cuteness often hides a lifetime of struggle. As science continues to shed light on the consequences of our breeding choices, researchers hope it leads to greater awareness—and ultimately, better lives for the animals we love.